North Bethany Stormwater Implementation Plan

North Bethany Area
Storm Implementation Plan
Jadene Torrent Stensland, PE
Senior Engineer
Water Resources
Jadene Torrent Stensland, PE
Senior Water Resources Engineer

OBJECTIVES
• BACKGROUND
• HISTORY
• DRAINAGE MASTER PLAN
• IMPLEMENTATION PLAN
• DESIGNS
• LIDA REDUCTIONS
• COST ESTIMATES

BACKGROUND
• Clean Water Services
• Washington County Special Service District
• Over 40 years of service
• Urban Sanitary and Stormwater Management
• Natural Resource Management
• Serve population 527,000+ residents

BACKGROUND
• North Bethany Sub Area
• Planning began over 10 years ago
• 800 acres, rural and ag
• 458 developable acres
• 3650 – 4750 new dwelling units
• Area of Distinction
Sustainability
Parks and Trails
Utilities Planning

North Bethany Area Map

History
• Drainage Master Plan
• Complete in December 2010
• Concept Planning Document
Design Criteria
Storm System concept layout
Preliminary Cost Estimates

Linear Storm Water System and Trails
Otak 2010 DMP
Greenworks 2009 Sketch

Implementation Plan
• North Bethany Implementation Plan
• Regional Facilities
• Major Conveyance System
• 30% Designs
• Cost Estimates

Regional Facility Sizing
Facility Concepts
1. Conventional Extended Dry Basin (round design)
2. Linear Extended Dry Basin (cascade design)
3. Implementation Options for Upstream LIDA

Conventional Extended Dry Basin
Regional Stormwater Facility Design Criteria
Design Criteria*
District
Maximum Depth
4.0 feet
Maximum Ponding Depth
3.0 feet
Freeboard
1.0 feet
Amended Soils
1.0 feet
Side Slopes (in treatment area) (H:V) 3:1
Overflow (Y/N)
Y
Native Plantings
Y
Fencing
Y
* Locate facilities outside of the
stream and vegetated corridor
(vc).
Extended Dry Basin

Facility Design Alternatives
Conventional Extended Dry Basin

Linear Extended Dry Basin
Regional Stormwater Facility Design Criteria
Design Criteria
Value
Maximum Depth
4.0 feet
Maximum Ponding Depth
3.0 feet
Freeboard
1.0 feet
Amended Soils
1.0 feet
Minimum Bottom Width
8 feet
Side Slopes (in treatment area) (H:V) 3:1
Bottom Slope 0.5%
Overflow (Y/N)
Y
Native Plantings
Y
Fencing
Y

Cascade Storm Water System
Otak 2010 DMP
Greenworks 2009 Sketch

Facility Design Alternatives
Linear Extended Dry Basin Example (cascade)

Facility Design Alternatives
Linear Extended Dry Basin Example (cascade)

3. Credit for Upstream LIDA
Areas Where Site LIDA is Required

3. Credit for Upstream LIDA
Assumptions for LIDA

2
3. Credit for Upstream LIDA
Impact to Regional Facility Size
1. Regional Facility Only (No LIDA)
2. LIDA Swale (Mandatory LIDA Areas Only)
3. LIDA Planter Current Requirements (Mandatory LIDA Areas Only)
4. LIDA Planter With Deeper Growing Medium (Mandatory LIDA
Areas Only)
5. LIDA Planter with Orifice to Meet Hydromod Stds. (Mandatory LIDA
Areas Only)
6. LIDA Planter Current Requirements (100% LIDA)
7. LIDA Planter with Orifice to Meet Hydromod Stds. (100% LIDA)
10000 15000 20000 25000 30000 35000 40000
Regional Facility Surface Area (sq-ft)

2
3. Credit for Upstream LIDA
Regional Facility Sizing Reduction Factors
Round Extended Detention Facility
Subbasin
BT3
BT2 and BT3
Impervious Area Treated
by Mandatory LIDA
(acres)
Facility Size (ft2)
0 20,146
7.0 16,074
0
45,705
11.0
39,611
Facility Area
Reduction/Impervious Acre
Treated by LIDA (ft2)
582
554
Linear Detention Facility
Subbasin
BT3
BT4
Impervious Area Treated
by Mandatory LIDA
(acres)
Facility Size (ft2)
0 28,758
7 25,800
0 4,816
3.4 3,440
Facility Area
Reduction/Impervious Acre
Treated by LIDA (ft2)
423
406

3. Credit for Upstream LIDA
Sizing Reduction Factors
Facility
ID
Subbasin
name
Total
contributing
area,
acres
Impervious
area,
acres
RSF top area
at 4-foot
depth,
sq ft
RSF top area
50% Implementation of
LIDA
sq ft
RSF top area
100% Implementation of
LIDA
sq ft
1 AB1 34.7 18.4 33,024 30,261 27,499
2 AB2 32.0 17.8 19,772 16,265 12,759
3 AB4 42.1 21.0 25,613 21,441 17,268
4 AB6 29.9 14.3 25,800 23,965 22,130
5 AB8 33.3 22.4 15,612 13,690 11,767
6 AB9 59.8 40.1 22,708 18,932 15,155
7 AB10 19.4 10.2 15,480 13,692 11,905
8 AB11 33.7 16.8 33,540 30,352 27,164
9 AB12 28.4 14.7 25,800 23,855 21,909
10
BT2 & BT3
combined
46.5 28.0 39,611 35,316 31,021
11a BT3 26.8 16.4 16,074 13,663 11,252
11b BT3 26.8 16.4 25,800 24,046 22,293
12 BT4 14.9 6.8 3,440 2,749 2,058
13 BT5 7.3 5.0 4,472 4,092 3,712
14 BT6 16.4 8.5 5,848 4,448 3,048
15 BT8 9.4 4.6 3,096 2,297 1,498
16 RU3 71.3 37.7 44,340 35,617 26,894
17 RU5 29.8 18.6 19,850 16,975 14,100

4. Analysis of Alternative LIDA
Configurations
2

2
LIDA
Configuration
4. Analysis of Alternative LIDA
Configurations
LIDA Planter as
Shown in the
Manual
LIDA Planter
Plus Additional
Growing Media
LIDA Planter
Plus Additional
Ponding
LIDA Planter Plus
Ponding and
Growing Media and
Unlined
LIDA Planter
Plus Growing
Media and
Unlined
LIDA Planter
Plus Ponding
and Growing
Media and Dead
Storage and
Unlined
LIDA Planter
Plus Ponding
and Growing
Media and No
Underdrain and
Unlined
Max Ponding
Depth (in) 6 6 12 12 6 12 12
Growing Media
Depth (in) 18 24 18 24 30 30 30
Drain Rock Layer
Depth (in) 12 12 12 12 12 15 12
Dead Storage (in) 3 3 3 3 3 6 12
Lined Yes Yes Yes No No No No
INFILT Value for
Facility (in/hr) NA NA NA 0.2 0.2 0.2 0.2
Sizing Factor
(%Impervious
Area) 31.5% 12% 16.5% 8.5% 7.25% 6.75% 6.4%
Total Facility
Depth (ft) 3.17 3.67 3.67 4.17 4.17 4.92 4.67

5. Results - Overview of Regional
Facility Layout

5. Results
• Required design elements:
• Must meet District D&C Standards.
• Footprint must match preliminary design.
• Outflow restriction (orifice) must match
preliminary design.
• Flexibility in design:
• Location of facility.
• The District is open to alternative designs that
meet minimum requirements.
• Modified LIDA to address water quantity.

5. Results (example Preliminary Design)

5. Results (preliminary design)

5. Results - Costs

Questions and
General Discussion
Contact:
Jadene Stensland, PE
Phone: 503-681-3662
Email: stenslandJ@CleanWaterServices.org